Conformal heat pipe assemblies

ABSTRACT

A heat pipe assembly includes walls having porous wick linings, an insulating layer coupled with at least one of the walls, and an interior chamber sealed by the walls. The linings hold a liquid phase of a working fluid in the interior chamber. The insulating layer is directly against a conductive component of an electromagnetic power conversion device such that heat from the conductive component vaporizes the working fluid in the porous wick lining of the at least one wall and the working fluid condenses at or within the porous wick lining of at least one other wall to cool the conductive component of the electromagnetic power conversion device. The assembly can be placed in direct contact with the device while the device is operating and/or experiencing time-varying magnetic fields that cause the device to operate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/670,460, which was filed on 11 May 2018, and the entire disclosure ofwhich is incorporated herein by reference.

FIELD

The subject matter described herein relates to heat pipes.

BACKGROUND

Electromagnetic (EM) power conversion devices generate heat duringoperation due to Joule heating. Examples of these types of devicesinclude electric machines such as motors and generators, inductors, andtransformers. The effectiveness of thermal management approach canrestrict the power density, the power per unit volume, and/or the powerper unit weight that can be achieved in these devices. Improving thethermal management approach can allow for increased amounts of electriccurrent in the conductors of the devices, without exceeding safeoperating temperature limits. Increasing the amount of current that canbe conducted in the conductors of the devices can allow for improvementsin the power densities of the devices.

One way to manage heat generated in devices are heat pipes. Some knownheat pipes are made from a conductive material, such as copper. Thisconductive material generates additional heat when in the presence ofhigh-frequency electromagnetic fields. As a result, the very heat pipesthat should operate to carry heat away from the devices (e.g., away fromconductive windings or coils of the devices) can generate additionalheat due to the changing electromagnetic fields near the heat pipes,leading to drop in power conversion efficiency, in addition topotentially increasing the temperatures.

BRIEF DESCRIPTION

In one embodiment, a heat pipe assembly includes plural connected wallshaving porous wick linings along the walls, an insulating layer coupledwith at least one of the walls on a side of the at least one wall thatis opposite of the porous wick lining of the at least one wall, and aninterior chamber disposed inside and sealed by the walls. The porouswick linings of the walls are configured to hold a liquid phase of aworking fluid in the interior chamber. The insulating layer of the atleast one wall is directly against a conductive component of anelectromagnetic power conversion device such that heat from theconductive component vaporizes the working fluid in the porous wicklining of the at least one wall and the working fluid condenses at orwithin the porous wick lining of at least one other wall to cool theconductive component of the electromagnetic power conversion device. Theassembly can be placed in direct contact with the device while thedevice is operating and/or experiencing time-varying magnetic fieldsthat cause the device to operate.

In one embodiment, a heat pipe system includes plural heat pipeassemblies configured to be disposed directly against conductivewindings of an electric motor to cool the windings. Each of the heatpipe assemblies includes plural connected walls having porous wicklinings along the walls. The walls include at least an interior wall, anouter wall, and a connecting wall that couples the interior wall withthe outer wall. Each of the heat pipe assemblies also includes aninterior chamber disposed inside and sealed by the walls. The porouswick linings of the walls are configured to hold a liquid phase of aworking fluid in the interior chamber. The interior walls of the heatpipe assemblies are configured to be located directly against theconductive windings of the motor such that heat from the conductivewindings vaporizes the working fluid in the porous wick linings of theinterior walls of the heat pipe assemblies. The working fluid condensesat or within the porous wick linings of the outer walls of the heat pipeassemblies to cool the conductive windings of the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The present inventive subject matter will be better understood fromreading the following description of non-limiting embodiments, withreference to the attached drawings, wherein below:

FIG. 1 illustrates one example of a cross-sectional view of a heat pipeassembly;

FIG. 2 illustrates a perspective view of conductive coils of a motorwith one embodiment of conformal heat pipe assemblies;

FIG. 3 is a perspective view of a portion of the conductive coils andheat pipe assemblies shown in FIG. 2;

FIG. 4 is a front view of a portion of the conductive coils and heatpipe assemblies shown in FIG. 2;

FIG. 5 illustrates a perspective view of the conductive coils of themotor shown in FIG. 2 with another embodiment of conformal heat pipeassemblies;

FIG. 6 is a perspective view of a portion of the conductive coils andheat pipe assemblies shown in FIG. 5;

FIG. 7 is a front view of a portion of the conductive coils and heatpipe assemblies shown in FIG. 5;

FIG. 8 illustrates a perspective view of the conductive coils of themotor shown in FIG. 2 with another embodiment of conformal heat pipeassemblies;

FIG. 9 is a perspective view of a portion of the conductive coils andheat pipe assemblies shown in FIG. 8;

FIG. 10 is a front view of a portion of the conductive coils and heatpipe assemblies shown in FIG. 8;

FIG. 11 is another perspective view of a portion of the conductive coilsand heat pipe assemblies shown in FIG. 8;

FIG. 12 illustrates a cross-sectional view of a coil of the motor shownin FIG. 2 and one embodiment of a heat pipe assembly;

FIG. 13 illustrates a cross-sectional view of a coil of the motor shownin FIG. 2 and another embodiment of a heat pipe assembly;

FIG. 14 illustrates a cross-sectional view of a coil of the motor shownin FIG. 2 and another embodiment of a heat pipe assembly;

FIG. 15 illustrates one embodiment of an end bell conformal heat pipeassembly;

FIG. 16 illustrates a first cross-sectional view of one embodiment of amotor housing heat pipe assembly;

FIG. 17 illustrates a second cross-sectional view of the motor housingheat pipe assembly shown in FIG. 16;

FIG. 18 illustrates a first cross-sectional view of one embodiment of arotor sleeve heat pipe assembly;

FIG. 19 illustrates a second cross-sectional view of the rotor sleeveheat pipe assembly shown in FIG. 18;

FIG. 20 illustrates a cross-sectional view of one embodiment of a rotorheat pipe assembly for an interior permanent magnet motor;

FIG. 21 illustrates a cross-sectional view of one embodiment of a rotorheat pipe assembly for an induction motor of a field wound motor;

FIG. 22 illustrates a cross-sectional view of one embodiment of atransformer windings or inductor windings heat pipe assembly;

FIG. 23 illustrates operation of one or more of the heat pipe assembliesshown in FIG. 8 in the motor shown in FIG. 2 that is disposed on amoving system;

FIG. 24 also illustrates operation of one or more of the heat pipeassemblies shown in FIG. 8 in the motor shown in FIG. 2 that is disposedon the moving system;

FIG. 25 also illustrates operation of one or more of the heat pipeassemblies shown in FIG. 8 in the motor shown in FIG. 2 that is disposedon the moving system; and

FIG. 26 illustrates a flowchart of one embodiment of a method forforming a heat pipe assembly for cooling an electric machine.

DETAILED DESCRIPTION

The subject matter described herein relates to heat pipes formed fromone or more materials having lower electrical conductivity than knownheat pipes (e.g., significantly lower than copper). For example, theconductivity of the material(s) used to form the heat pipes describedherein can be at least one, and may be two or more orders of magnitudesmaller than copper (in one embodiment). One or more embodiments of theheat pipes described herein can be formed from titanium, which has asignificantly lower electrical conductivity than copper. The heat pipescan be coated conformally with high thermal conductivity ceramicinsulation materials via electrophoretic deposition (EPD) for electricalisolation, which can maintain the thermal performance of the heat pipeswhile enhancing insulation properties of the heat pipes.

One embodiment of the inventive subject matter described herein providesa method involving coating a surface of the heat pipe with a ceramicmaterial including a nitride, via an electrophoretic process, to form afirst coating. The method further includes contacting the first coatingdeposited by the electrophoretic process with a thermoset resin to forma second coating; and curing the second coating to form the electricallyinsulating coating including the ceramic material dispersed in a polymermatrix. A suitable thermally conductive ceramic material includesaluminum nitride, boron nitride, diamond, aluminum oxide, orcombinations thereof. A suitable thermoset resin in the ceramic matrixinclude an epoxy, a siloxane, polyester, polyurethane, cyanate ester,polyimide, polyamide, polyamideimide, polyesterimide, polyvinyl ester,or combinations thereof. Additionally, with additive manufacturing,conformal heat pipes can be form-fitted to practically any winding orcoil shape of a machine. Finally, making the heat pipes out ofhigh-strength titanium allows for the replacement of structural elementsin heat pipes, such as slot wedges, end-bells, and/or motor housings,leading to dual-purpose thermal-mechanical structures with enhancedperformance at reduced weight.

Thermal management in electrical machines typically involves heatextraction outside the magnetically active zones, by employingapproaches such as liquid or air-cooled heat sinks. This approach may betermed ‘remote cooling’. That is, the heat generated in the machine isconducted across several zones from the source to the sink, before theheat can be extracted. In an electric motor, for example, the heatgenerated in the copper conductors may be conducted through strandinsulation, turn insulation, potting resin, ground-wall insulation,winding-core interface, core laminations, core-housing interface andfins, before the heat can be rejected to the surrounding working fluid.These various zones have limited thermal conductivities (e.g., windings˜0.5 W/m-K, insulation layers ˜0.15 W/m-K, potting resin ˜0.2 W/m-K,laminations ˜25 W/m-K). Therefore, this approach limits the amount ofheat that can be extracted and consequently limits the current that canbe sustained in the devices.

Improvements to the above approach are also employed when higherperformance and power densities are desired, such as by bringing theworking fluid closer to the conductors when feasible (e.g., using hollowconductors and flowing the heat-extracting working fluid directly nearthe heat generating conductors in the devices). This approach, termed‘embedded cooling’ or ‘direct conductor cooling,’ currently is employedin high voltage machines, where the insulation layers are significantlythicker and severely limit heat extraction via conventional approaches.This approach relies on clean, dielectric working fluids and needsadditional infrastructure such as flow distribution manifolds, hoses andfilters, for accomplishing the flow, adding to the overall cost andcomplexity of the design and reducing the overall power density.

Heat pipes or interior chambers are seeing increasing use to addresssimilar heat extraction challenges in other applications such aselectronics cooling. These devices operate on the principle ofphase-change heat transfer in sealed tubes or enclosures, and whenproperly designed, efficiently carry heat from remote, hard to reachheat sources to the nearby, convenient heat sinks where the heat can bemore easily extracted with minimal or reduced temperature drops.Properly designed heat pipes therefore operate as “thermalsuperconductors” in a thermal management system. The employment andacceptance of heat pipes in EM power conversion applications, however,has been limited for several reasons, such as commercially availableheat pipes are typically made up of copper. When such heat pipes areused close to high frequency EM fields, significant eddy current inducedheat generation results, causing an overall drop in efficiency andperformance. Additionally, the area available for the windings or coilsin these devices is compact and the winding profiles are non-standard(i.e., the windings are not always circular or rectangular).

Some known heat pipes or interior chambers may only be available ineither rectangular or cylindrical tube configurations, further limitinguse of these types of heat pipes or interior chambers in theseapplications. Additionally, owing to the voltage difference between thewindings which are at the designed electrical potential, and the heatpipes which are at ground potential, electrical insulation may need tobe employed. Typical electrical insulation materials such as NOMEX,KAPTON, mica and fiberglass, are also thermally insulating, cutting downthe overall effectiveness of the heat pipes when used near the windings.

One or more embodiments of the inventive subject matter described hereinaddress many, if not all, of the shortcomings of copper heat pipesdescribed above. Additionally, form fitted, structural-thermal dualpurpose mechanical elements can be formed for further improving thethermal performance of the heat pipes, along with overall weightreduction. The inventive heat pipe assemblies described herein can beused as heat pipes and interior chambers for cooling conductive coils ofelectric motors (including motors having concentrated windings and/ordistributed windings). The assemblies can be conformal interior chamberend-bell assemblies used in motors to cool end-turns of motor windingsof the motors. The assemblies can be conformal in that the assemblieshave an exterior shape and/or size that conforms to (e.g., iscomplementary to or matches) the shape of at least a portion of anelectrical machine, e.g. the end windings.

The assemblies can form housings of electrical machines, with thehousing having interior chambers that conform to shapes of theelectrical machines. One embodiment of the assemblies includes a sleeveor endplate of a rotor in a motor that includes a conformal interiorchamber that cools the rotor. The assemblies can provide for rotorcooling for internal permanent magnets (IPM), surface permanent magnets(SPM), for induction machines (IM) which are singly or doubly excited,switched reluctance machines (SRM), synchronous reluctance machines(SynRM), or for field wound machines (FWM). The assemblies can providefor cooling of transformer and/or inductor windings with a heat pipe orinterior chamber built or formed into a bobbin of the transformer, withan optional extension to a heat sink of the heat pipe that assists indrawing heat out and away from the windings.

While many examples of the uses of the heat pipe assemblies aredescribed herein, not all uses of the heat pipe assemblies are limitedto these examples. The heat pipe assemblies may be used to cool othermagnetic devices, machines, or applications.

In one embodiment, the heat pipe assemblies are formed from titanium ortitanium alloys. The heat pipe assemblies can be formed by additivelymanufacturing the shapes of the assemblies to conform with the shapes ofthe devices that are cooled by the assemblies. For example, theassemblies can be created using three-dimensional (3D) printing, rapidprototyping (RP), direct digital manufacturing (DDM), selective lasermelting (SLM), electron beam melting (EBM), direct metal laser melting(DMLM), or the like.

The heat pipe assemblies can be formed from another material in place ofor in addition to titanium. For example, the heat pipe assemblies can beformed from another material that is thermally conductive yetelectrically resistive, such as stainless steel.

The heat pipe assemblies can be placed or formed in direct contact withthe conductive windings of the magnetic devices described herein. Thiscontrasts with some known heat pipe assemblies, which can require thatinsulation be placed between the exterior surface(s) of the heat pipeassemblies and the conductive windings of the magnetic devices. The heatpipe assemblies can be placed within the time-varying electro-magneticfields that are generated to cause the devices to operate, in contrastwith some known heat pipe assemblies, which are positioned outside ofthese fields. By applying the heat pipe assemblies directly to thesource of heat in these devices, a significant thermal performanceadvantage may be realized relative to some known heat pipe assemblies.

One or more embodiments of the inventive subject matter described hereinrelates to integrated thermal and mechanical assemblies that can be usedin devices for cooling conductive windings of the devices, includingthree-dimensional printed conformal interior chambers.

FIG. 1 illustrates one example of a cross-sectional view of a heat pipeassembly 100. The assembly 100 is shown in FIG. 1 to describe the basicoperation of how the conformal heat pipe assemblies described hereinremove thermal energy from an electrical and/or mechanical heat source(e.g., the conductive windings of an electro-magnetic device, such as amotor, inductor, transformer, induction heating coil, or the like) insteady and/or unsteady cooling conditions.

The assembly 100 includes a vapor housing 102 with low thermalresistance. The housing 102 can be formed using additive manufacturing(e.g., three-dimensional printing) and/or can be formed from a materialhaving low thermal resistance and low electric conductivity (e.g.,titanium, stainless steel, etc.). The vapor housing 102 defines andencloses an interior chamber 104. This chamber 104 may be hermeticallysealed from the outside environment so that working fluid inside thechamber 104 (e.g., water) is not able to pass out of the chamber 104through the housing 102 and/or is not able to enter the chamber 104through the housing 102.

The housing 102 is defined by several walls 106, 108, 110, 112 thatextend around and enclose the chamber 104. The walls 106, 108, 110, 112are provided merely as one example of how the various heat pipeassemblies described herein can operate to remove heat from anelectro-magnetic device. The number, size, and/or arrangement of thewalls 106, 108, 110, 112 can change based on the shape of theelectro-magnetic device to which the heat pipe assembly is to conform.Additionally, using additive manufacturing support walls may be built inspecific places within the vapor space 104 if needed, to mechanicallysupport the outer housing 102 and provide additional rigidity to thestructure. The support walls can be configured to allow for thecontinuous flow of the vapor to offer minimal or reduced blockage.

Optionally, one or more of the exterior surfaces of the wall 106, 108,110, and/or 112 can include or be coupled with an insulation layer 116.This insulation layer 116 can be formed from a dielectric material, amaterial that is not thermally conductive (or that is less thermallyconductive than the wall 106, 108, 110, and/or 112), and/or a materialthat is not electrically conductive (or that is less electricallyconductive than the wall 106, 108, 110, and/or 112). Examples ofmaterials that the insulation layer 116 can be formed from include apolyamide, KAPTON, or NOMEX. In one embodiment, the insulation layer 116is formed on one or more of the walls 106, 108, 110, and/or 112 usingelectrophoretic deposition. Alternatively, another deposition techniqueis used.

In one embodiment, the interior surfaces of one or more of the walls106, 108, 110, and/or 112 include, are formed from, or are lined with aporous wick structure or lining 114. The porous wick structure 114 canbe formed using additive manufacturing and may be formed from sinteredpowder. Alternatively, the porous wick structure 114 can be formed usinganother technique and/or from another material. The porous wickstructure 114 can line the entire interior surfaces of the chamber 104and can hold liquid working fluid. Optionally, not all walls may includethe insulating layer 116 and/or the porous wick structure 114. Forexample, one or more of the walls may not include the wick structure114, or a portion of at least one wall may not include the wickstructure 114. As another example, one or more of the walls may notinclude the insulating layer 116, or a portion of at least one wall maynot include the insulating layer 116. Optionally, one or more interiorsupport columns or posts may extend from one wall to an opposite wall tomechanically support the walls away from each other.

The housing 102 conducts thermal energy from an electro-magnetic devicethrough the walls 106, 108, 110, and/or 112, depending on which wall isnext to the device. In some embodiments, multiple walls 106, 108, 110,112 may be in contact with the same or different devices at the sametime. In one example of operation of the assembly 100, the wall 108 maybe in direct contact with a source of heat, such as the conductivewindings of the device.

As the wall 108 absorbs thermal energy, the wall 108 transfers thethermal energy to a working fluid (e.g., water, ammonia, etc.) that isheld within the chamber 104 and/or within pores of the porous wickstructure 114 along the wall 108. This working fluid may be in a liquidstate in the porous wicking structure 114. As the working fluid absorbsthe thermal energy, the fluid changes phase from a liquid phase to avapor phase and moves into the interior chamber 104. As the workingfluid moves into the chamber 104 and/or toward the cooler walls 106,110, and/or 112, the working fluid cools and condenses (e.g., changesfrom a vapor phase into a liquid phase). The liquid phase of the fluidthen recirculates back into to the chamber 104 through gravity and/orcapillary forces, where the fluid again absorbs thermal energy from thewall 108, thereby continuing the evaporation-condensation cycle.

For example, the sealed chamber 104 can hold the liquid phase of theworking fluid and the gaseous phase of the working fluid inthermodynamic equilibrium. When heat is introduced into the chamber 104(e.g., at one or more walls 106, 108, 110, 112) and heat is removed fromthe chamber 104 (e.g., at one or more other walls 106, 108, 110, 112located farther from the heat source), a very efficient heat transferprocess occurs. This process involves the heat entering the wall 106,108, 110, or 112 and reaching the liquid working fluid in the porouswick lining 114 of the wall 106, 108, 110, or 112. The liquid workingfluid is at least partially vaporized by the heat, and the vapor movesto where the vapor can condense, such as the interior of the chamber 104and/or another wall 106, 108, 110, 112 located farther from the heatsource. The vapor condenses back into a liquid phase and, upon doing so,releases heat back into the wall(s) 106, 108, 110, 112 located fartherfrom the heat source. The liquid working fluid enters back into theporous wick lining 114 and can be drawn back toward the interior chamber104 by capillary action (e.g., capillary wicking forces).

FIG. 2 illustrates a perspective view of conductive coils 200 of a motor202 with one embodiment of conformal heat pipe assemblies 204. FIG. 3 isa perspective view of a portion of the conductive coils 200 and heatpipe assemblies 204. FIG. 4 is a front view of a portion of theconductive coils 200 and heat pipe assemblies 204. The motor 202 is oneexample of an electro-magnetic power conversion device described herein.Only a ring portion 206 of a stator of the motor 202 is shown in FIG. 2,and the motor 202 may include additional components. The ring portion206 can represent a portion of the inside or inner diameter of thestator. The ring 206 includes several conductive coils or windings 200that when passing current through, produce magnetic fields whichinteract with the rotor (not shown), causing it to move.

The coils 200 can generate heat during operation of the motor 202. Thisheat can be dissipated or otherwise removed from the coils 200 by theheat pipe assemblies 204. The heat pipe assemblies 204 are L-shapedbodies in the illustrated embodiment. The heat pipe assemblies 204include interior portions 210 that extend between neighboring coils 200of the motor 202 and exterior portions 208 that are disposed outside ofthe coils 200 (e.g., are not located between the coils 200). Theinterior portions 210 are elongated in axial directions that areparallel to a center axis or axis of rotation 216 of the motor 202. Theexterior portions 208 are elongated in radial directions that areperpendicular to the center axis or axis of rotation 216 of the motor202. In the illustrated embodiment, the exterior portions 208 of theheat pipe assemblies 204 all are located on one side of the ring portion206 of the stator of the motor 202. Additionally, the exterior portionsof the heat pipe assemblies 204 all extend radially outward (e.g., awayfrom the center axis or axis of rotation 216 of the motor 202) in theillustrated embodiment.

The heat pipe assemblies 204 can include interior chambers 104 havingporous wick linings 114 with working fluid therein, as shown in FIG. 1.The heat pipe assemblies 204 can help to rapidly cool the coils 200 byremoving heat from the coils 200, as described above in connection withthe heat pipe assembly 100 shown in FIG. 1. For example, opposing walls106, 108 in the interior portions 210 of the heat pipe assemblies 204can be in direct contact with neighboring coils 200. Heat from the coils200 vaporizes working fluid held in the porous wick linings 114 of thewalls 106, 108, and the vapor working fluid then can move within theinterior chambers 104 of the heat pipe assemblies 204 into the exteriorportions 208 of the heat pipe assemblies 204 where there is less heat.The vapor working fluid can then condense back into the liquid workingfluid (as described below), which then flows or is pulled (e.g., viacapillary action) back into the porous wick linings 114 of the interiorportions 210.

The walls 106, 108 of the interior portion 210 of each of the heat pipeassemblies 204 are in direct contact with the coils 200 that are onopposite sides of the heat pipe assembly 204, as shown in FIG. 4. Forexample, no additional material other than the material that forms thewalls 106, 108 may be disposed between the wall 106 and/or 108 and thenearest coil 200.

The exterior portions 208 of the heat pipe assemblies 204 includeseveral fins 212. These fins 212 may be hollow, elongated extensionsthat outwardly project from the interior chambers 104 of the exteriorportions 208 of the heat pipe assemblies 204. This can allow for theworking fluid working fluid in the interior chambers 104 of the heatpipe assemblies 204 to flow into the fins 212. In operation, heat fromthe coils 200 can vaporize the liquid phase of the working fluid in theporous wick lining 114 in the plates 208 of the interior portion 210 ofthe heat pipe assembly 204 that are adjacent to or otherwise in contactwith the coils 200. The vaporized coolant can move in the portion of theinterior chamber 104 that is in the interior portion 210 of the heatpipe assembly 204 to the portion of the interior chamber 104 that is inthe exterior portion 208 of the heat pipe assembly 204.

The vaporized working fluid can condense in the portion of the interiorchamber 104 that is in the exterior portion 208 of the heat pipeassembly 204. At least some of the vaporized working fluid can flow intothe hollow fins 212 of the exterior portion 208 of the heat pipeassembly 204 to reduce the time needed for the vaporized working fluidto condense. This can rapidly cool the heat generated by the coils 200.The condensed working fluid can then flow back into the porous wicklining 114 in the interior portion 210 of the heat pipe assembly 204. Asdepicted, the heat pipe assembly 204 interfaces with the fins 212consistent with an air-cooled arrangement. Optionally, the heat pipeassemblies 204 can interface with a liquid heat exchanger consistentwith a liquid-cooled arrangement instead. In an alternative embodiment,the fins 212 can be separate entities and are attached to the heat pipeusing epoxy, solder or a similar bonding operation ensuring thermalcommunication between the heat pipe body and fins.

FIG. 5 illustrates a perspective view of the conductive coils 200 of themotor 202 with another embodiment of conformal heat pipe assemblies 504.FIG. 6 is a perspective view of a portion of the conductive coils 200and heat pipe assemblies 504. FIG. 7 is a front view of a portion of theconductive coils 200 and heat pipe assemblies 504.

The heat pipe assemblies 504 are L-shaped bodies in the illustratedembodiment. The heat pipe assemblies 504 include interior portions 510that extend between neighboring coils 200 of the motor 202 and exteriorportions 508 that are disposed outside of the coils 200 (e.g., are notlocated between the coils 200). The interior portions 510 are elongatedin axial directions that are parallel to a center axis or axis ofrotation 216 of the motor 502. The exterior portions 508 are elongatedin radial directions that are perpendicular to the center axis or axisof rotation 216 of the motor 202. In the illustrated embodiment, theexterior portions 508 of the heat pipe assemblies 504 all are located onone side of the ring portion 206 of the stator of the motor 202.Additionally, the exterior portions of the heat pipe assemblies 504 allextend radially inward (e.g., toward the center axis or axis of rotation216 of the motor 202) in the illustrated embodiment, in contrast to theheat pipe assemblies 204 shown in FIGS. 2 through 4.

The heat pipe assemblies 504 can include interior chambers 104 havingporous wick linings 114 with working fluid therein, as shown in FIG. 1.The heat pipe assemblies 504 can help to rapidly cool the coils 200 byremoving heat from the coils 200, as described above. For example,opposing walls 106, 108 in the interior portions 510 of the heat pipeassemblies 504 can be in direct contact with neighboring coils 200. Heatfrom the coils 200 vaporizes working fluid held in the porous wicklinings 114 of the walls 106, 108, and the vapor working fluid then canmove within the interior chambers 104 of the heat pipe assemblies 504into the exterior portions 508 of the heat pipe assemblies 504 wherethere is less heat. At least some of the vapor working fluid can enterthe fins 212 of the exterior portion 508 of the heat pipe assemblies504, as described above. The vapor working fluid can then condense backinto the liquid working fluid, which then flows or is pulled (e.g., viacapillary action) back into the porous wick linings 114 of the interiorportions 510.

The walls 106, 108 of the interior portion 510 of each of the heat pipeassemblies 504 are in direct contact with the coils 200 that are onopposite sides of the heat pipe assembly 504, as shown in FIG. 8. Forexample, no additional material other than the material that forms thewalls 106, 108 may be disposed between the wall 106 and/or 108 and thenearest coil 200.

FIG. 8 illustrates a perspective view of the conductive coils 200 of themotor 202 with another embodiment of conformal heat pipe assemblies 804.FIG. 9 is a perspective view of a portion of the conductive coils 200and heat pipe assemblies 804. FIG. 10 is a front view of a portion ofthe conductive coils 200 and heat pipe assemblies 804. FIG. 11 isanother perspective view of a portion of the conductive coils 200 andheat pipe assemblies 804.

The heat pipe assemblies 804 are L-shaped bodies in the illustratedembodiment. The heat pipe assemblies 804 include interior portions 810that extend between neighboring coils 200 of the motor 202 and exteriorportions 808 that are disposed outside of the coils 200 (e.g., are notlocated between the coils 200). The interior portions 810 are elongatedin axial directions that are parallel to a center axis or axis ofrotation 216 of the motor 502. The exterior portions 808 are elongatedin radial directions that are perpendicular to the center axis or axisof rotation 216 of the motor 202. In the illustrated embodiment, theexterior portions 808 of the heat pipe assemblies 804 are located onopposite sides of the ring portion 206 of the stator of the motor 202.For example, the exterior portions 808 can alternate between the sidesof the ring portion 206 such that heat pipe assemblies 804 that neighboreach other have exterior portions 808 on opposite sides of the ringportion 206. The heat pipe assemblies 804 that neighbor each other canhave interior portions 810 that contact opposite sides of the same coil200. Additionally, the exterior portions of the heat pipe assemblies 804all extend radially outward (e.g., away from the center axis or axis ofrotation 216 of the motor 202).

The heat pipe assemblies 804 can include interior chambers 104 havingporous wick linings 114 with working fluid therein, as shown in FIG. 1.The heat pipe assemblies 804 can help to rapidly cool the coils 200 byremoving heat from the coils 200, as described above. For example,opposing walls 106, 108 in the interior portions 810 of the heat pipeassemblies 804 can be in direct contact with neighboring coils 200. Heatfrom the coils 200 vaporizes working fluid held in the porous wicklinings 114 of the walls 106, 108, and the vapor working fluid then canmove within the interior chambers 104 of the heat pipe assemblies 804into the exterior portions 808 of the heat pipe assemblies 804 wherethere is less heat. At least some of the vapor working fluid can enterthe fins 212 of the exterior portion 808 of the heat pipe assemblies804, as described above. The vapor working fluid can then condense backinto the liquid working fluid, which then flows or is pulled (e.g., viacapillary action) back into the porous wick linings 114 of the interiorportions 810.

The walls 106, 108 of the interior portion 810 of each of the heat pipeassemblies 804 are in direct contact with the coils 200 that are onopposite sides of the heat pipe assembly 804, as shown in FIGS. 9, 10,and 11. For example, no additional material other than the material thatforms the walls 106, 108 may be disposed between the wall 106 and/or 108and the nearest coil 200.

FIG. 12 illustrates a cross-sectional view of a coil 200 of the motor202 and one embodiment of a heat pipe assembly 1204. The cross-sectionalview can represent a two-dimensional plane that is orientedperpendicular to the axis of rotation 216 of the motor 202. The motor202 has the coils 200 arranged as concentrated windings in theillustrated embodiment. The heat pipe assembly 1204 can represent one ormore of the heat sink assemblies 204, 504, 804 described above. Thecross-sectional view of FIG. 12 only shows a cross-section of theinterior portion of the heat pipe assembly 1204. As shown, the heat pipeassembly 1204 has the hollow interior chamber 104, with the walls 106,108 being adjacent to and/or in contact with the coil 200. The interiorportion of the heat pipe assembly 1204 has a rectangular cross-sectionalshape in the illustrated embodiment. The ring portion 206 of the statorof the motor 202 optionally can include a topstick 1200, which can bemagnetic or non-magnetic in different embodiments.

FIG. 13 illustrates a cross-sectional view of a coil 200 of the motor202 and another embodiment of a heat pipe assembly 1304. Thecross-sectional view can represent a two-dimensional plane that isoriented perpendicular to the axis of rotation 216 of the motor 202. Themotor 202 has the coils 200 arranged as concentrated windings in theillustrated embodiment. The heat pipe assembly 1304 can represent one ormore of the heat sink assemblies 204, 504, 804 described above. Thecross-sectional view of FIG. 13 only shows a cross-section of theinterior portion of the heat pipe assembly 1304. As shown, the heat pipeassembly 1304 has the hollow interior chamber 104, with walls of theassembly 1304 being adjacent to and/or in contact with the coil 200. Theinterior portion of the heat pipe assembly 1304 has a T-shapedcross-sectional shape in the illustrated embodiment. This shape providesfor a radial portion 1300 of the interior chamber 104 being elongated ina direction that is perpendicular to the axis of rotation 216 and acircumferential portion 1302 of the interior chamber 104 being elongatedin a direction that encircles or that otherwise does not intersect theaxis of rotation 216. For example, the interior chamber 104 can beelongated in an orthogonal direction to the axis of rotation 216. Thisshape of the heat pipe assembly 1304 can provide for more contactbetween the coil 200 and the heat pipe assembly 1304 relative to theembodiment shown in FIG. 12. This can result in heat being more rapidlytransferred from the coil 200 to the heat pipe assembly 1304 to morerapidly cool the coil 200. Optionally, the heat pipe assembly 1304 canoperate as an integrated topstick of the motor.

FIG. 14 illustrates a cross-sectional view of a coil 200 of the motor202 and another embodiment of a heat pipe assembly 1404. Thecross-sectional view can represent a two-dimensional plane that isoriented perpendicular to the axis of rotation 216 of the motor 202. Themotor 202 has the coils 200 arranged as distributed windings in theillustrated embodiment. The ring portion 206 of the stator of the motor202 optionally can include the topstick 1200 described above.

The heat pipe assembly 1404 can represent one or more of the heat sinkassemblies 204, 504, 804 described above. The cross-sectional view ofFIG. 14 only shows a cross-section of the interior portion of the heatpipe assembly 1404. As shown, the heat pipe assembly 1404 has the hollowinterior chamber 104, with the walls 106, 108 of the assembly 1404 beingadjacent to and/or in contact with the coil 200. The interior portion ofthe heat pipe assembly 1404 has a rectangular cross-sectional shape inthe illustrated embodiment. While the interior portion of the heat pipeassembly 1204 shown in FIG. 12 is elongated in a direction that radiallyextends toward or away from the axis of rotation 216 of the motor 202,the interior portion of the heat pipe assembly 1404 is elongated in acircumferential direction that encircles the axis 216.

FIG. 15 illustrates one embodiment of an end bell conformal heat pipeassembly 1500. The heat pipe assembly 1500 is formed into or is formedas an end bell 1502 that couples with the motor 202. The end bell 1502couples with a stator housing 1504 of a stator 1506 of the motor 202.The end bell 1502 includes recesses 1508 having shapes that conform tothe shapes of the coils 200 of the motor 202. For example, the recesses1508 may have U-shapes or other concave shapes that separately receivethe separate coils 200 of the motor 202.

The end bell 1502 can be formed (e.g., using additive manufacturing) toinclude heat sink assemblies 1510 in the end bell 1502. The assemblies1510 can be shaped to match the curved shape of the coils 200, as shownin FIG. 15. For example, the convex shapes of the coils 200 can extendinto the concave shapes of the assemblies 1510. These assemblies 1510include the interior chamber 104 that is defined and enclosed by theinterior porous wick linings described above. For example, one curvedwall 1512 of the assembly 1510 can be an evaporator wall of the assembly1510 that includes a porous wick lining and an opposite curved or flatwall 1514 of the assembly 1510 can be a condenser wall that includesanother porous wick lining. The end bell 1502 optionally can include agap pad 1516, which can be a flexible, thermally conductive materialthat engages the coils 200. This gap pad 1516 can engage the coils 200without imparting mechanical damage to the end turns of the coils 200(e.g., the visible portions of the coils 200 in FIG. 15), while alsothermally conducting heat from the coils 200 to the assembly 1510.

In operation, heat from the end turns of the coils 200 is received bythe evaporator walls 1512 of the assemblies 1510. This heat evaporatesliquid working fluid in the porous wick linings of the evaporator walls1512. The vaporized working fluid moves toward the condenser wall 1514,where the working fluid condenses to form liquid working fluid. Heatfrom the end turns of the coils 200 is drawn out from the coils 200 bythis evaporation and condensation. The heat pipe assembly 1500 that isformed into the end bell 1502 of the motor 202 can be used alone or incombination with one or more other heat pipe assemblies described hereinto rapidly cool the conductive coils of a motor.

FIG. 16 illustrates a first cross-sectional view of one embodiment of amotor housing heat pipe assembly 1600. FIG. 17 illustrates a secondcross-sectional view of the motor housing heat pipe assembly 1600. Theview shown in FIG. 16 is along a two-dimensional plane that is parallelto or that includes the axis of rotation 216 of the motor 202. The viewshown in FIG. 17 is along another two-dimensional plane that isperpendicular to the axis of rotation 216. As shown, the motor 202 caninclude the end bell 1502. Optionally, this end bell 1502 can be formedas the end bell conformal heat pipe assembly 1500 described above.

The heat pipe assembly 1600 is formed into or is formed as an outerhousing 1602 of the motor 202. The heat pipe assembly 1600 can be formedusing additive manufacturing. The heat pipe assembly 1600 can be used tocool the motor 202, and can be used in combination with one or more ofthe other heat pipe assemblies described herein. The housing 1602includes an interior wall 1604 and an opposite wall 1606 with a sealedinterior chamber 1608 between the walls 1604, 1606. The walls 1604, 1606can include the porous wick linings described herein. A working fluidcan be disposed inside the chamber 1608 and/or the pores of the walls1604, 1606.

The interior wall 1604 can be directly adjacent to the stator housing1504 to cool the stator housing 1504. The opposite wall 1606 optionallyincludes elongated fins 1610 that outwardly project away from the statorhousing 1504. The fins 1610 can be hollow extensions of the interiorchamber 1608 such that the working fluid can flow inside the fins 1610.In operation, the heat from the stator housing 1504 evaporates liquidworking fluid in the pores of the porous lining of the wall 1604. Thevaporized working fluid radially flows away from the wall 1604 inwardinto the interior chamber 1608 and optionally toward the portions of theinterior chamber 1608 that are inside the fins 1610. The fins 1610permit the vaporized working fluid to move farther away from the sourceof heat (e.g., the motor), and providing several fins 1610 allowssmaller portions of the vaporized working fluid to be separately cooled.These features can permit the vaporized working fluid to rapidlycondense by transferring the heat from the motor 202 outside of theassembly 1600, and thereby rapidly cool the motor 202.

As shown in FIG. 17, the heat pipe assembly 1600 optionally can includeone or more support posts 1700. The posts 1700 are structural membersthat assist in separating the walls 1604, 1606 from each other bymechanically supporting the wall 1606 outside of the wall 1604. Theposts 1700 can be formed from the same materials and/or formed usingadditive manufacturing. Optionally, the posts 1700 can divide theinterior chamber 1608 up into several, smaller chambers 1608. The posts1700 can include a porous wick lining 114 to aid in moving the condensedworking fluid back from the side where the fluid condenses to the sidewhere the fluid evaporates upon exposure to heat.

FIG. 18 illustrates a first cross-sectional view of one embodiment of arotor sleeve heat pipe assembly 1800. FIG. 19 illustrates a secondcross-sectional view of the rotor sleeve heat pipe assembly 1800. Theview shown in FIG. 18 is along a two-dimensional plane that is parallelto or that includes the axis of rotation 216 of the motor 202. The viewshown in FIG. 19 is along another two-dimensional plane that isperpendicular to the axis of rotation 216. A rotor 1802 of the motor 202(shown in FIG. 16) is disposed inside the stator 1506 (shown in FIG.15). The rotor 1802 is coupled with an elongated shaft 1804, and boththe rotor 1802 and the shaft 1804 rotate around or about the axis ofrotation 216.

The heat pipe assembly 1800 can be formed as a sleeve and/or end plateon the rotor 1802. The heat pipe assembly 1800 can be disposed betweenthe rotor 1802 and the stator 1506 to cool the rotor 1802 and optionallythe stator 1506. The heat pipe assembly 1800 includes a sleeve portion1808 and an end plate portion 1806. The sleeve portion 1808 is elongatedin directions that are parallel to the axis 216, while the end plateportion 1806 is elongated in directions that are perpendicular to theaxis 216. The end plate portion 1806 can be formed as a circular platewith an opening through which the shaft 1804 extends. In FIG. 18, onlyone half of the sleeve and end plate portions 1808, 1806 is shown.

The heat pipe assembly 1800 can be formed using additive manufacturing.The heat pipe assembly 1800 can be used to cool the rotor 1802, and canbe used in combination with one or more of the other heat pipeassemblies described herein. The portions 1806, 1808 of the heat pipeassembly 1800 include an interior wall 1810 and an opposite wall 1812with a sealed interior chamber 1814 between the walls 1810, 1812. Thewalls 1810, 1812 can include the porous wick linings described herein. Aworking fluid can be disposed inside the chamber 1814 and/or the poresof the walls 1810, 1812.

The interior wall 1810 can be directly adjacent to the exterior surfacesof the rotor 1802, as shown in FIG. 18. The end plate portion 1806optionally includes elongated fins 1610 that outwardly project away fromthe outer wall 1812 of the end plate portion 1806. As described above,the fins 1610 can be hollow extensions of the interior chamber 1814 suchthat the working fluid can flow inside the fins 1610. In operation, theheat from the rotor 1802 evaporates liquid working fluid in the pores ofthe porous lining of the wall 1810. The vaporized working fluid radiallyflows (in the sleeve portion 1808) and axially flows (in the end plateportion 1806) away from the wall 1810 toward the portions of theinterior chamber 1814 and optionally toward the portions of the interiorchamber 1814 that are inside the fins 1610. The vaporized working fluidcan then condense and return to the pores in the wall 1810. In oneembodiment, centrifugal forces can assist in returning the working fluidto the side of the heat pipe assembly where evaporation of the workingfluid occurs.

As shown in FIG. 19, the heat pipe assembly 1800 optionally can includeone or more support posts 1700. As described above, the posts 1700 arestructural members that assist in separating the walls 1810, 1812 fromeach other by mechanically supporting the wall 1812 outside of the wall1810. The posts 1700 can be formed from the same materials and/or formedusing additive manufacturing. Optionally, the posts 1700 can divide theinterior chamber 1814 up into several, smaller chambers 1814.

FIG. 20 illustrates a cross-sectional view of one embodiment of a rotorheat pipe assembly 2000 for an interior permanent magnet motor. The viewshown in FIG. 20 is along a two-dimensional plane that is perpendicularto the axis of rotation of the rotor of the interior permanent magnetmotor. Only a portion of a rotor 2001 and shaft 2003 of the interiorpermanent magnet motor is shown in FIG. 20.

The heat pipe assembly 2000 is formed as a rectangular box in which apermanent magnet 2006 of the interior permanent magnet motor is placed.Several heat pipe assemblies 2000 can be provided, such as one assembly2000 for each permanent magnet in the interior permanent magnet motor.The heat pipe assembly 2000 can be formed using additive manufacturing.The heat pipe assembly 2000 can be used to cool the magnets 2006. Theheat pipe assembly 2000 includes an interior wall 2002 and an oppositewall 2004 with a sealed interior chamber 2006 between the walls 2002,2004. The walls 2002, 2004 can include the porous wick linings describedherein. A working fluid can be disposed inside the chamber 2006 and/orthe pores of the walls 2002, 2004.

The interior wall 2002 can be directly adjacent to the exterior surfacesof the magnet 2006. In operation, the heat from the magnet 2006evaporates liquid working fluid in the pores of the porous lining of theinterior wall 2002. The vaporized working fluid radially flows away fromthe interior wall 2002 toward the interior chamber 2008 and the outerwall 2004. This can help draw heat away from and cool the magnet 2006.The vaporized working fluid can condense and return to the interior wall2002, as described herein.

FIG. 21 illustrates a cross-sectional view of one embodiment of a rotorheat pipe assembly 2100 for an induction motor of a field wound motor.The view shown in FIG. 21 is along a two-dimensional plane that isperpendicular to an axis of rotation 2126 of the rotor 2102 of theinduction motor. Only a portion of a rotor 2102 is shown in FIG. 21.

The rotor 2102 includes several conductive rods or bars 2104 that areelongated in directions that are parallel to the axis of rotation 2126of the rotor 2102. This axis 2126 is oriented perpendicular to the viewof FIG. 21 (e.g., into and out of the page of FIG. 21). These bars 2104are placed in openings in the rotor 2102. Several heat pipe assemblies2100 can be formed around the bars 2104. The heat pipe assemblies 2100can be in direct contact with the bars 2104. For example, each heat pipeassembly 2100 can be formed as a cylindrical sleeve in which one of thebars 2104 are positioned, with the heat pipe assembly 2100 and the bar2104 placed into an opening in the rotor 2102, as shown in FIG. 21.

The heat pipe assemblies 2100 can be formed using additivemanufacturing. The heat pipe assemblies 2100 can be used to cool thebars 2104, which can heat up during operation due to the changingmagnetic field to which the bars 2104 are exposed to rotate the rotor2102. Although only five of the bars 2104 are shown as including a heatpipe assembly 2100, optionally, a different number or all the bars 2104can be provided with a heat pipe assembly 2100.

Each of the heat pipe assemblies 2100 can include an interior wall 2106and an opposite outer wall 2108 with a sealed interior chamber 2110between the walls 2106, 2108. The walls 2106, 2108 can include theporous wick linings described herein. A working fluid can be disposedinside the chamber 2110 and/or the pores of the walls 2106, 2108. Theinterior wall 2106 can be directly adjacent to the exterior surfaces ofthe bar 2104. In operation, the heat from the bar 2104 evaporates liquidworking fluid in the pores of the porous lining of the interior wall2106. The vaporized working fluid radially flows away from the interiorwall 2106 toward the interior chamber 2110 and the outer wall 2108. Thiscan help draw heat away from and cool the bar 2104. The vaporizedworking fluid can condense and return to the interior wall 2106, asdescribed herein.

FIG. 22 illustrates a cross-sectional view of one embodiment of atransformer windings or inductor windings heat pipe assembly 2200. Theheat pipe assembly 2200 can be used to cool conductive windings 2202 ofa transformer or inductor device 2204. The windings 2202 can behelically wrapped around a bobbin 2206, and the heat pipe assembly 2200can be at least partially located between the windings 2202 and thebobbin 2206. A magnetic core 2208 of the device 2204 is positioned suchthat the windings 2202 extend around opposing sections of the magneticcore 2208 that are separated by an insulative gap. Alternatively, theheat pipe assembly 2200 can form the bobbin 2206. For example, the heatpipe assembly 2200 can be formed as a cylindrical body about which thewindings 2202 are wrapped.

As shown, the heat pipe assembly 2200 can be formed to include ridges2201 that radially extend away from a center axis of the heat pipeassembly 2200 or bobbin 2206. These ridges can be sized and positionedto receive different windings 2202. The ridges increase the surface areawhere the windings 2202 engage the heat pipe assembly 2200, which canincrease the rate at which heat is thermally transferred from thewindings 2202 to the heat pipe assembly 2200. The ridges optionally canprovide a guide for where the windings 2202 are to be positioned duringmanufacture of the transformer.

In operation, the windings 2202 can become heated due to the varyingmagnetic field that is generated around the core 2208 from the passageof current through the windings 2202. The heat pipe assembly 2200 canhelp to cool these windings 2202. The heat pipe assembly 2200 can wraparound the bobbin 2206 between the windings 2202 and the bobbin 2206.The heat pipe assembly 2200 includes opposing inner and outer walls2210, 2212, with a sealed interior chamber 2214 located between thewalls 2210, 2212. The walls 2210, 2212 can include the porous wicklinings 114, as described herein, with a working fluid in the pores ofthe linings 114 and the chamber 2214. The walls 2212 may be in directcontact with the windings 2202. For example, there may not be any othermaterial between the walls 2212 and the windings 2202.

The heat pipe assembly 2200 also can include a chamber extension 2216,which is an extension of the interior chamber 2214 that is not disposedbetween the windings 2202 and the bobbin 2206. In the illustratedembodiment, this extension 2216 is formed by portions of the walls 2210,2212 and the chamber 2214 that extend along the length of the bobbin2206 outside of the windings 2202, as shown in FIG. 22. The walls 2210,2212 can encircle the bobbin 2206 such that the heat pipe assembly 2200forms a cylindrical sleeve in which the bobbin 2206 is disposed. Thechamber extension 2216 can be part of this cylindrical sleeve thatextends outside of the windings 2202.

The heat pipe assemblies 2200 can be formed using additivemanufacturing. The heat pipe assemblies 2200 can be used to cool thewindings 2202, which can heat up during operation of the device 2204. Inoperation, the heat from the windings 2202 evaporates liquid workingfluid in the pores of the porous lining of the wall 2212 and potentiallyin the pores of the wall 2210. The vaporized working fluid axially flowsin the chamber 2214 in directions along the length of the bobbin 2206toward the chamber extension 2216. For example, the vaporized workingfluid increases the gas pressure inside the chamber 2214 in locationsbetween the windings 2202 and the bobbin 2206. This increased pressurecan cause the vaporized working fluid to flow in the chamber 2214 alongthe length of the bobbin 2206 toward the chamber extension 2216.

The temperature inside the chamber extension 2216 may be reducedrelative to the temperature inside the chamber 2214 between the windings2202 and the bobbin 2206. This can be due to the heated windings 2202being farther from the chamber extension 2216. The cooler temperaturesin the chamber extension 2216 can cause the vaporized working fluid tocondense, which transfers thermal energy out of the heat pipe assembly2200 and helps to cool the windings 2202. The liquid working fluid canthen flow back into the pores of the walls 2210, 2212 and into thechamber 2214 in locations between the windings 2202 and the bobbin 2206to continue cooling the windings 2202.

FIGS. 23 through 25 illustrate operation of one or more of the heat pipeassemblies 804 in the motor 202 that is disposed on a moving system.While the description and illustration focuses on the heat pipeassemblies 804, the description also can apply to other heat pipeassemblies described herein. The motor 202 may be onboard a movingsystem, such as a vehicle (e.g., an aircraft such as a fixed wingairplane or a helicopter) that experiences different gravitational andother forces due to acceleration of the vehicle. For example, duringtakeoff of an aircraft (shown in FIG. 23) from the ground, the motor 202can experience acceleration forces a+g due to both the pull of gravitytoward the ground (e.g., g) and acceleration of the aircraft away fromthe ground (e.g., a). These forces can cause the working fluid in theheat pipe assemblies 804 to be drawn to one wall or side of the interiorchambers inside the assemblies 804 than another.

For example, the heat pipe assemblies 804 below the motor 202 (relativeto the direction in which the vehicle is acceleration, or below themotor 202 in FIG. 23) can have the working fluid pulled away fromlocations that are between the conductive coils 200 of the motor 202.This can result in decreased cooling of the coils 200 by the heat pipeassemblies 804 located below the motor 202 (relative to the heat pipeassemblies 804 operating without the acceleration forces a and/orgravity forces g acting on the working fluid). But, the heat pipeassemblies 804 above the motor 202 (relative to the direction in whichthe vehicle is acceleration, or above the motor 202 in FIG. 23) can havethe working fluid pulled into locations that are between the conductivecoils 200 of the motor 202. This can result in increased cooling of thecoils 200 by the heat pipe assemblies 804 located above the motor 202(relative to the heat pipe assemblies 804 operating without theacceleration forces a and/or gravity forces g acting on the workingfluid).

The net effect of the decreased cooling of half of the heat pipeassemblies 804 and the increased cooling of the other half of the heatpipe assemblies 804 can result in the coils 200 being cooled at the samerate and/or by the same amount that the coils 200 would have been cooledwithout the influence of the acceleration forces a and/or gravity forcesg acting on the working fluid. For example, the increased cooling by theheat pipe assemblies 804 above the motor 202 can counteract and cancelout the decreased by the heat pipe assemblies 804 below the motor 202.

As another example, during constant velocity cruising of the aircraft(shown in FIG. 24), the aircraft may be moving in directions that aremore parallel to the ground than away from the ground (e.g., takeoff) ortoward the ground (e.g., landing). The motor 202 can experience gravityforces g due to the pull of gravity toward the ground. These forces cancause the working fluid in the heat pipe assemblies 804 on the lowerhalf of the motor 202 (e.g., below a bisecting plane 2400) to be drawnto one wall or side of the interior chambers inside the assemblies 804than another. For example, the heat pipe assemblies 804 below the plane2400 can have the working fluid pulled away from locations that arebetween the conductive coils 200 of the motor 202. This can result indecreased cooling of the coils 200 by the heat pipe assemblies 804located below the motor 202 (relative to the heat pipe assemblies 804operating without the gravity forces g acting on the working fluid).But, the heat pipe assemblies 804 above the plane 2400 can have theworking fluid pulled into locations that are between the conductivecoils 200 of the motor 202. This can result in increased cooling of thecoils 200 by the heat pipe assemblies 804 located below the plane 2400(relative to the heat pipe assemblies 804 operating without the gravityforces g acting on the working fluid).

The coils of the motor can be wound with parallel paths such that thetop half of the motor forms one parallel path and the lower half of themotor forms a second parallel path. By adding parallel winding paths tothe motor, the net effect of the decreased cooling of half of the heatpipe assemblies 804 and the increased cooling of the other half of theheat pipe assemblies 804 can result in the coils 200 being cooled at thesame rate and/or by the same amount that the coils 200 would have beencooled without the influence of the gravity forces g acting on theworking fluid. For example, the increased cooling by the heat pipeassemblies 804 above the plane 2400 can counteract and cancel out thedecreased by the heat pipe assemblies 804 below the plane 2400. Thisleveling of temperature occurs due to the positive temperaturecoefficient on the electrical resistivity of copper as a function oftemperature.

If the coils on the top half of the motor were at a lower temperaturethan those in the lower half of the motor, the electric currents beingconducted in the coils are redistributed in that the amount of currentconducted in the coils in the top half of the motor increases whiledecreasing the amount of current conducted in the coils in the lowerhalf of the motor. This occurs because the current is conducted moreeasily in the lower temperature half of the motor than in the hotterlower half of the motor. This would result in the temperature of thecooler coils on the top half of the motor increasing (due to morecurrent being conducted in these coils) and the temperature of thewarming coils on the bottom half of the motor decreasing (due to lesscurrent being conducted in these coils). In effect, the combination ofparallel winding paths and heat-pipe cooling forms a “self-leveling”process which cancels out the increased or decreased cooling (asapplicable) due to the orientation of the heat pipe assemblies.

While only two parallel winding paths of coils are shown and described(e.g., top and bottom half coils), the motor windings may be segmentedinto a different number of parallel winding paths up to and includingwhere each motor winding is in parallel with all others. For example,the windings on the top half of the motor may be one parallel conductivepath and the windings in the bottom half of the motor may be another,different parallel conductive path. Alternatively, more than twoparallel paths may be provided.

As another example, during cruising of the aircraft, the aircraft mayaccelerate in a direction that is parallel to the ground (shown in FIG.25). During this lateral or horizontal acceleration, the motor 202 canexperience acceleration forces a and gravitational forces g in differentdirections. The acceleration forces a can pull on the working fluid inone direction (e.g., opposite of the Accelerating Cruise arrow shown inFIG. 25) while the gravity forces g pull on the working fluid in aperpendicular direction (e.g., toward the ground). These forces cancause the working fluid in the heat pipe assemblies 804 to be drawn indifferent directions.

For example, the heat pipe assemblies 804 that are along a leading sideof the motor 202 (e.g., the right side of the motor 202 in FIG. 25) andthat are above the bisecting plane 2400 can have both the accelerationforces a and the gravity forces g pull the working fluid in theseassemblies 804 to locations between the coils 200. This can result insignificantly improved cooling of the coils 200 relative to other heatpipe assemblies 804. Conversely, the heat pipe assemblies 804 that arealong the opposite, trailing side of the motor 202 (e.g., the left sideof the motor 202 in FIG. 25) and that are below the bisecting plane 2400can have both the acceleration forces a and the gravity forces g pullthe working fluid in these assemblies 804 to locations away from thecoils 200. This can result in significantly decreased cooling of thecoils 200 relative to other heat pipe assemblies 804.

The heat pipe assemblies 804 that are along the leading side of themotor 202 and that are below the bisecting plane 2400 can have theacceleration forces a pull the working fluid in these assemblies 804 tolocations between the coils 200, but the gravity forces g pull theworking fluid away from locations between the coils 200. This can resultin improved cooling of the coils 200 relative to other heat pipeassemblies 804 other than the heat pipe assemblies 804 that are abovethe plane 2400 and along the leading side of the motor 202. The heatpipe assemblies 804 that are along the trailing side of the motor 202and that are above the bisecting plane 2400 can have the gravity forcesg pull the working fluid in these assemblies 804 to locations betweenthe coils 200, but also can have the acceleration forces a pull theworking fluid in these assemblies 804 to locations that are not betweenthe coils 200. This can result in improved cooling of the coils 200relative to heat pipe assemblies 804 other than the heat pipe assemblies804 that are above the plane 2400 and along the leading side of themotor 202.

The net effect of the different amounts of cooling different quadrantsof the heat pipe assemblies 804 can result in the coils 200 being cooledat the same rate and/or by the same amount that the coils 200 would havebeen cooled without the influence of the acceleration forces a and/orgravity forces g acting on the working fluid.

FIG. 26 illustrates a flowchart of one embodiment of a method 2600 forforming a heat pipe assembly for cooling an electric machine. The method2600 can be used to create one or more of the heat pipe assemblies shownand/or described herein. Two or more of the operations described inconnection with the method 2600 can be performed at the same time (e.g.,concurrently or simultaneously), or may be performed sequentially.

At 2602, an interior portion of a heat pipe assembly is formed. Theinterior portion of the heat pipe assembly can define part of a vaporchamber that is shaped to be positioned against or close to conductiveportions of an electric machine. For example, the interior portion canbe sized to fit between coils of a stator, can be sized as an end bellto fit against the coils of the stator, can be sized to be placedoutside of the stator of the motor, can be sized to be placed betweenthe rotor and the stator of the motor, can be sized to be placed aroundor between magnets inserted in the rotor and the surrounding portion ofthe rotor in the motor, can be sized to be placed around or betweenconductive rods inserted in the rotor and the surrounding portion of therotor in the motor, can be sized to be placed around or againstconductive coils of a transformer, or the like. The interior portion canbe formed to have a porous wick structure on one or more interiorsurfaces of the interior portion. As described above, this wickstructure can hold a working fluid to help cool the electric machine.The interior portion of the heat pipe assembly can be created usingadditive manufacturing in one embodiment.

Optionally, the interior portion can be formed to have one or moreinterior support posts. As described above, these posts can mechanicallysupport opposite sides of the heat pipe assembly from moving toward eachother during operation of the electric machine.

At 2604, an exterior portion of the heat pipe assembly is formed. Theexterior portion can be formed with the interior portion, such as byadditively manufacturing the interior and exterior portions at the sametime or during the same printing session. Alternatively, the interiorand exterior portions can be formed at different times. The exteriorportion also can include the interior porous wick structure to hold orhelp condense the working fluid described above.

The exterior portion may be formed to be away from the source of heatthat vaporizes the working fluid in the interior portion of the heatpipe assembly. For example, the interior and exterior portions can beformed in an L-shape, with the interior portion shaped to fit betweenneighboring coils of the stator of the motor and the exterior portiondisposed outside of (e.g., not between) the coils. As another example,the exterior portion can be a portion of the heat pipe assembly that isfarther from the coils in the end bell heat pipe assembly, that isfarther from the magnets or conductive rods in the rotor than theinterior portion, that is farther from the rotor that the interiorportion, or the like. In one embodiment, the exterior portion can beformed as an extension of a transformer bobbin to allow the workingfluid to move away from the coils of the transformer and cool in theexterior portion of the heat pipe assembly.

In one embodiment, a heat pipe assembly includes plural connected wallshaving porous wick linings along the walls, an insulating layer coupledwith at least one of the walls on a side of the at least one wall thatis opposite of the porous wick lining of the at least one wall, and aninterior chamber disposed inside and sealed by the walls. The porouswick linings of the walls are configured to hold a liquid phase of aworking fluid in the interior chamber. The insulating layer of the atleast one wall is directly against a conductive component of anelectromagnetic power conversion device such that heat from theconductive component vaporizes the working fluid in the porous wicklining of the at least one wall and the working fluid condenses at orwithin the porous wick lining of at least one other wall to cool theconductive component of the electromagnetic power conversion device.

Optionally, the conductive component includes one or more conductivewindings of the electromagnetic power conversion device such that theheat from the one or more conductive windings vaporizes the workingfluid in the porous wick lining of the interior wall and the workingfluid condenses at or within the porous wick lining of the outer wall tocool the one or more conductive windings of the electromagnetic powerconversion device.

Optionally, the walls form an elongated interior portion of the interiorchamber that is located between and directly adjacent to neighboringconductive coils of the one or more conductive windings.

Optionally, the interior portion of the interior chamber is elongatedalong an axis of rotation of the electromagnetic power conversiondevice.

Optionally, the walls also form an elongated exterior portion of theinterior chamber that is located outside of the conductive coils.

Optionally, the exterior portion of the interior chamber is elongated indirections that are perpendicular to an axis of rotation of theelectromagnetic power conversion device.

Optionally, the assembly also includes elongated fins outwardlyextending from the exterior portion.

Optionally, the elongated exterior portion of the interior chamber iselongated in a direction radially oriented toward an axis of rotation ofthe electromagnetic power conversion device.

Optionally, the elongated exterior portion of the interior chamber iselongated in a direction radially oriented away from an axis of rotationof the electromagnetic power conversion device.

Optionally, the interior portion of the interior chamber has arectangular cross-sectional shape in locations between the neighboringconductive coils.

Optionally, the interior portion of the interior chamber extends betweenand contacts the neighboring conductive coils on multiple differentplanes of the conductive coils.

Optionally, the interior portion of the interior chamber has a T-shapedcross-sectional shape.

Optionally, the interior portion of the interior chamber is locatedbetween and contacts opposing surfaces of the neighboring conductivecoils that are concentrated windings of an electric motor.

Optionally, the interior portion of the interior chamber is locatedbetween and contacts opposing surfaces of the neighboring conductivecoils that are distributed windings of an electric motor.

Optionally, the interior portion of the interior chamber has an H-shapedcross-sectional shape.

Optionally, the assembly also includes an end bell that couples withconductive windings of a motor as the electromagnetic power conversiondevice. The walls and the interior chamber can be located within the endbell.

Optionally, the walls are located outside of and directly contact astator of a motor that is the electromagnetic power conversion device.

Optionally, the walls form elongated fins that radially project awayfrom an axis of rotation of the motor, and wherein the interior chamberextends into the fins.

Optionally, the assembly also includes support posts located between thewalls to structurally support the walls away from each other.

Optionally, the walls form a rotor sleeve and end plate in which a rotorof a motor is located as the electromagnetic power conversion device.

Optionally, the rotor sleeve formed by the walls encircles the rotoraround an axis of rotation of the rotor.

Optionally, the end plate formed by the walls is oriented perpendicularto an axis of rotation of the rotor.

Optionally, the end plate includes elongated fins that axially projectaway from the end plate in directions parallel to the axis of rotation.The interior chamber can extend into the elongated fins.

Optionally, the walls extend around a permanent magnet in an interiorpermanent magnet motor as the electromagnetic power conversion device.

Optionally, the walls extend around a magnet in an induction motor of afield wound motor as the electromagnetic power conversion device.

Optionally, the walls extend around a bobbin of a transformer as theelectromagnetic power conversion device, with the walls and interiorchamber disposed between conductive windings of the transformer and thebobbin.

Optionally, the walls form an extension of the interior chamber thatextends along a length of the bobbin but is not located between thebobbin and the conductive windings of the transformer.

In one embodiment, a heat pipe system includes plural heat pipeassemblies configured to be disposed directly against conductivewindings of an electric motor to cool the windings. Each of the heatpipe assemblies includes plural connected walls having porous wicklinings along the walls. The walls include at least an interior wall, anouter wall, and a connecting wall that couples the interior wall withthe outer wall. Each of the heat pipe assemblies also includes aninterior chamber disposed inside and sealed by the walls. The porouswick linings of the walls are configured to hold a liquid phase of aworking fluid in the interior chamber. The interior walls of the heatpipe assemblies are configured to be located directly against theconductive windings of the motor such that heat from the conductivewindings vaporizes the working fluids in the porous wick linings of theinterior walls of the heat pipe assemblies. The working fluid condensesat or within the porous wick linings of the outer walls of the heat pipeassemblies to cool the conductive windings of the motor.

Optionally, the walls of the heat pipe assemblies form elongatedinterior portions of the interior chambers that are located between anddirectly adjacent to neighboring conductive windings of the one or moreconductive windings. The walls of the heat pipe assemblies also can formelongated exterior portions of the interior chambers that are locatedoutside of the conductive windings of the motor.

Optionally, the interior portions of the interior chambers are elongatedin directions that are parallel to an axis of rotation of the motor.

Optionally, the exterior portions of the interior chambers are elongatedin directions that are perpendicular to an axis of rotation of themotor.

Optionally, at least one of the heat pipe assemblies also includeselongated fins outwardly extending from the exterior portions of theheat pipe assemblies.

Optionally, the conductive windings of the motor extend along a circularring around an axis of rotation of the motor. The exterior portions ofthe heat pipe assemblies all can be located on a single side of thering.

Optionally, the conductive windings of the motor extend along a circularring around an axis of rotation of the motor. The exterior portions of afirst group of the heat pipe assemblies can be located on a first sideof the ring and the exterior portions of a second, non-overlapping groupof the heat pipe assemblies can be located on an opposite second side ofthe ring.

Optionally, the exterior portions of the heat pipe assemblies areelongated in directions that are oriented radially inward toward an axisof rotation of the motor.

Optionally, the exterior portions of the heat pipe assemblies areelongated in directions that are oriented radially outward from an axisof rotation of the motor.

Optionally, the heat pipe assemblies assist in self-leveling atemperature differential of the conductive windings of the electricmotor during operation of the electric motor by receiving more electriccurrent in a first set of the conductive windings that are cooler due tothe working fluid in a corresponding first set of the heat pipeassemblies being directed to locations closer to the conductive windingsin the first set of the conductive windings due to one or more ofgravitational forces or acceleration forces, and by a different, secondset of the conductive windings of the electric motor that are hotterreceiving less electric current due to the working fluid in acorresponding second set of the heat pipe assemblies being directed tolocations farther from the conductive windings in the second set of theconductive windings due to the one or more of gravitational forces oracceleration forces.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventivesubject matter without departing from its scope. While the dimensionsand types of materials described herein are intended to define theparameters of the inventive subject matter, they are by no meanslimiting and are exemplary embodiments. Many other embodiments will beapparent to one of ordinary skill in the art upon reviewing the abovedescription. The scope of the inventive subject matter should,therefore, be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled. Inthe appended claims, the terms “including” and “in which” are used asthe plain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects. Further, thelimitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. § 112(f), unless and until such claim limitations expresslyuse the phrase “means for” followed by a statement of function void offurther structure.

This written description uses examples to disclose several embodimentsof the inventive subject matter, including the best mode, and also toenable one of ordinary skill in the art to practice the embodiments ofinventive subject matter, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe inventive subject matter is defined by the claims, and may includeother examples that occur to one of ordinary skill in the art. Suchother examples are intended to be within the scope of the claims if theyhave structural elements that do not differ from the literal language ofthe claims, or if they include equivalent structural elements withinsubstantial differences from the literal languages of the claims.

The foregoing description of certain embodiments of the presentinventive subject matter will be better understood when read inconjunction with the appended drawings. The various embodiments are notlimited to the arrangements and instrumentality shown in the drawings.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of the present invention arenot intended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features. Moreover, unlessexplicitly stated to the contrary, embodiments “comprising,”“comprises,” “including,” “includes,” “having,” or “has” an element or aplurality of elements having a particular property may includeadditional such elements not having that property.

What is claimed is:
 1. A heat pipe assembly comprising: plural connectedwalls having porous wick linings along the walls; an insulating layercoupled with at least one of the walls on a side of the at least onewall that is opposite of the porous wick lining of the at least onewall; and an interior chamber disposed inside and sealed by the walls,wherein the porous wick linings of the walls are configured to hold aliquid phase of a working fluid in the interior chamber, wherein theinsulating layer of the at least one wall is directly against aconductive component of an electromagnetic power conversion device suchthat heat from the conductive component vaporizes the working fluid inthe porous wick lining of the at least one wall and the working fluidcondenses at or within the porous wick lining of at least one other wallto cool the conductive component of the electromagnetic power conversiondevice.
 2. The heat pipe assembly of claim 1, wherein the conductivecomponent includes one or more conductive windings of theelectromagnetic power conversion device such that the heat from the oneor more conductive windings vaporizes the working fluid in the porouswick lining of the at least one wall and the working fluid condenses ator within the porous wick lining of the at least one other wall to coolthe one or more conductive windings of the electromagnetic powerconversion device.
 3. The heat pipe assembly of claim 2, wherein thewalls form an elongated interior portion of the interior chamber that islocated between and directly adjacent to neighboring conductive coils ofthe one or more conductive windings.
 4. The heat pipe assembly of claim3, wherein the interior portion of the interior chamber is elongatedalong an axis of rotation of the electromagnetic power conversiondevice.
 5. The heat pipe assembly of claim 3, wherein the walls alsoform an elongated exterior portion of the interior chamber that islocated outside of the conductive coils.
 6. The heat pipe assembly ofclaim 5, wherein the exterior portion of the interior chamber iselongated in directions that are perpendicular to an axis of rotation ofthe electromagnetic power conversion device.
 7. The heat pipe assemblyof claim 5, further comprising elongated fins outwardly extending fromthe exterior portion.
 8. A heat pipe system comprising: plural heat pipeassemblies configured to be disposed directly against conductivewindings of an electric motor to cool the windings, each of the heatpipe assemblies including: plural connected walls having porous wicklinings along the walls, the walls including at least an interior wall,an outer wall, and a connecting wall that couples the interior wall withthe outer wall; and an interior chamber disposed inside and sealed bythe walls, wherein the porous wick linings of the walls are configuredto hold a liquid phase of a working fluid in the interior chamber,wherein the interior walls of the heat pipe assemblies are configured tobe located directly against the conductive windings of the motor suchthat heat from the conductive windings vaporizes the working fluids inthe porous wick linings of the interior walls of the heat pipeassemblies, and the working fluid condenses at or within the porous wicklinings of the outer walls of the heat pipe assemblies to cool theconductive windings of the motor.
 9. The system of claim 8, wherein thewalls of the heat pipe assemblies form elongated interior portions ofthe interior chambers that are located between and directly adjacent toneighboring conductive windings of the one or more conductive windings,the walls of the heat pipe assemblies also forming elongated exteriorportions of the interior chambers that are located outside of theconductive windings of the motor.
 10. The system of claim 9, wherein theinterior portions of the interior chambers are elongated in directionsthat are parallel to an axis of rotation of the motor.
 11. The system ofclaim 9, wherein the exterior portions of the interior chambers areelongated in directions that are perpendicular to an axis of rotation ofthe motor.
 12. The system of claim 9, further comprising elongated finsoutwardly extending from the exterior portions of the heat pipeassemblies.
 13. The system of claim 9, wherein the conductive windingsof the motor extend along a circular ring around an axis of rotation ofthe motor, and wherein the exterior portions of a first group of theheat pipe assemblies are located on a first side of the ring and theexterior portions of a second, non-overlapping group of the heat pipeassemblies are located on an opposite second side of the ring.
 14. Thesystem of claim 8, wherein the heat pipe assemblies assist inself-leveling a temperature differential of the conductive windings ofthe electric motor during operation of the electric motor by receivingmore electric current in a first set of the conductive windings that arecooler due to the working fluid in a corresponding first set of the heatpipe assemblies being directed to locations closer to the conductivewindings in the first set of the conductive windings due to one or moreof gravitational forces or acceleration forces, and by a different,second set of the conductive windings of the electric motor that arehotter receiving less electric current due to the working fluid in acorresponding second set of the heat pipe assemblies being directed tolocations farther from the conductive windings in the second set of theconductive windings due to the one or more of gravitational forces oracceleration forces.
 15. A heat pipe assembly comprising: pluralconnected walls extending around interior chambers, the walls havingporous wick linings along the walls that are configured to hold a liquidphase of a working fluid in the interior chambers, the walls formingelongated interior portions of the interior chambers that are locatedbetween neighboring conductive windings of a motor, the walls alsoforming elongated exterior portions of the interior chambers that arelocated outside the conductive windings of the motor; and an insulatinglayer coupled with at least one of the walls on a side of the at leastone wall that is opposite of the porous wick lining of the at least onewall, the insulating layer of the at least one of the walls directlyabutting at least one of the conductive windings of the motor such thatheat from the conductive component vaporizes the working fluid in afirst porous wick lining of the porous wick linings and a second porouswick lining of the porous wick linings receives a condensed phase of theworking fluid that was vaporized to cool the conductive component of theelectromagnetic device.
 16. The heat pipe assembly of claim 15, whereinthe elongated interior portions of the interior chambers are elongatedin directions that are parallel to an axis of rotation of the motor. 17.The heat pipe assembly of claim 15, wherein the elongated exteriorportions of the interior chambers are elongated in directions that areperpendicular to an axis of rotation of the motor.
 18. The heat pipeassembly of claim 15, wherein the elongated exterior portions of theinterior chambers are elongated in directions extend radially outwardfrom an axis of rotation of the motor.
 19. The heat pipe assembly ofclaim 15, wherein the elongated exterior portions of the interiorchambers are elongated in directions extend radially inward toward anaxis of rotation of the motor.
 20. The heat pipe assembly of claim 15,wherein the elongated exterior portions of the interior chambers arelocated on one side of a ring portion of a stator of the motor.